See Michael Lamm's book - The Great Camaro. There is a picture of a JL8 rear axle on page 67. The calipers appear painted. Page 64 also has a picture, but more difficult to tell if they are painted.
John Hooper's book, The 1969 Camaro Reference Book, has pictures of JL8 calipers on page 123 & 127. Appears painted, but sorta hard to confirm 100%.